A fundamental problem facing investigators in the application of retroviral technology to the treatment of human diseases continues to be the inability to efficiently transduce long-lived and reconstituting hematopoietic stem cells. Although this problem remains a significant focus of at least two laboratories involved in this program (Williams and Hoffman/Srour), the goals in this program are to exploit current technology to efficiently insert a variety of genes into transplantable and relatively short-lived multipotent progenitor cells. This focus has been arrived at after a number of preliminary meetings by members of the program group in which we discussed the potential of these cells to be transduced efficiently, the likelihood that the introduced genetic material would be expressed (based on work by this group and other investigators), and the availability of technology at Indiana University which would allow these cells to be obtained in enriched fashion. A second goal of the proposed studies is the practical application of gene transfer technology to the treatment of cancer. Although several years away, this program addresses the use of retroviral-mediated gene transfer to treat three different human tumors which are currently not successfully treated by standard chemotherapy protocols. These tumors include: childhood high-grade brain gliomas; neuroectodermal tumors of childhood; and chronic myelogenous leukemia in adults. The goals in each case are to approach the treatment of these tumors with innovative protocols which utilize retroviral vectors, including the use of drug-resistance genes to dose intensify, the use of immune modulation via gene transfer of class II MHC antigens, and the transfer of growth regulating genes into the environment of bone marrow cells in vitro which have been previously shown to affect the growth of normal and malignant hematopoietic cells. A final goal of the program is to continue basic work to improve the efficiency of gene transfer into the most primitive hematopoietic stem cells, which is a requisite for any future application of gene transfer technology which requires changing the phenotype of bone marrow-derived cells for the lifetime of the transplanted individual. The major theme of the program is the effective use of retroviral vectors for the phenotypic manipulation f bone marrow cells. This theme is approached in different specific ways by each project and targets both murine and human bone marrow. The focus of the program is such that information obtained by one project will be useful (and in several cases required) to the progress of other investigators.